The present invention relates in general to erosion control blocks, and more particularly to the type of erosion control block that can be cabled together with other similar blocks, and installed as a mattress by a crane and spreader bar.
There are numerous types and shapes of erosion control blocks for covering a ground area to prevent erosion of the underlying earth material. An erosion control block is generally constructed of a heavy material, such as concrete, so that the block remains stationary when water flows around or over the block. The shape of erosion control blocks can be made so as to be interlocking, or interengaging, and facilitate the hydraulic stability of the block installed in a waterway, or the like. Interengaging erosion control blocks can be constructed similar to that shown in U.S. Pat. No. 5,484,230 by Rudloff. Interlocking erosion control blocks can be constructed in a manner similar to that shown in U.S. Pat. No. 5,556,228 by Smith. The interlocking type of block prevents lateral removal thereof from another similar block, when moved in any lateral direction. Interengaging erosion control blocks generally provide stability between blocks in one lateral direction, but not a lateral direction perpendicular thereto. The flexibility of interlocking blocks is generally less than that of the interengaging blocks.
Some erosion control blocks are simply installed by workmen carrying the blocks from a pallet and installing the blocks in a side-by-side relationship. A geotextile is generally layed on the ground before the installation of the erosion control blocks. Depending upon the terrain and other factors, the blocks may simply be interengaged or interlocked together. In other situations, the erosion control blocks are installed in an interengaged or interlocking manner, and thereafter cables are threaded therethrough to provide farther stability to the matrix or mattress of blocks.
In accordance with other installation techniques, a matrix of erosion control block can be interengaged or interlocked together at the plant, and cabled as a mattress so as to form a flexible unit. In erosion control blocks fabricated for cabling, two or more cable channels are formed through the blocks so that cables can be threaded therethrough. The mattresses can be lifted by the cables and loaded onto a truck or train. The mattress can then be lifted by the cables off a transport truck, or the like, by a large crane and spreader bar assembly, and moved to the site to be protected from erosion. A cellular concrete mattress of erosion control blocks typically includes a matrix of six blocks by thirty-two blocks, which generally measures eight foot by forty foot. A number of such mattresses are installed together so as to provide full coverage over the terrain to be protected from erosion.
The cabling material is generally a synthetic rope that is threaded through the blocks in an X-direction, as well as a Y-direction, to form the mattress. When installing multiple mattresses of erosion control blocks together, the blocks forming the border of the adjacent mattress are anchored together by splicing the cables. In other words, the end of a cable threaded through the border block of one mattress is spliced to the end of the other cable threaded through the border block of the adjacent mattress. The splicing of the two cable ends includes the utilization of an aluminum sleeve into which the end of each cable is inserted, and then two crimps are made to fasten the cable ends together via the sleeve. It can be appreciated that the border blocks of adjacent mattresses can not be installed in contact with each other, otherwise there would be no room to carry out the splicing operation. As such, the edge or border of one mattress is generally spaced two inches from the border blocks of the adjacent mattress.
The space between mattresses of erosion control blocks creates a channel through which water can flow in an unimpeded manner. Depending upon the environmental conditions, the flow of water through this channel between the mattresses of erosion control blocks can carry soil with it, thereby forming a pocket under the geotextile material. This is especially prevalent where the mattresses of erosion control blocks are laid on inclined channel banks, where the water flow from the top to the bottom of the grade is swift. When erosion of soil under the geotextile occurs, failures in the erosion control system can occur. In some instances, a sufficient amount of soil is removed through erosion under the geotextile, such that the overlying blocks become suspended by the cables, and bridge the void area. Due to the weight of the blocks, the cables can often break and thereby cause a catastrophic erosion condition.
From the forgoing, it can be seen that a need exists for a technique for cabling together erosion control blocks so as to avoid water flow channel areas between the mattresses. Another need exists for a erosion control block itself which facilitates the splicing of cables therebetween as well as reduces the speed or volume per unit time of the water that flows in the channel between mattresses. Yet another need exists for a design of erosion control blocks which, when installed adjacent to each other a distance sufficient to allow splicing of cables therebetween, the flow of water between the border blocks is circuitous, thereby reducing possibilities of erosion. A further need exists for a block design where a space between engaged blocks exists, but when the blocks are lifted by a cable to a catenary position, the block edges engage and load forces between blocks are distributed over a larger area of engagement.
An erosion control block and the method of installation thereof is described below. In one embodiment, the erosion control block is fabricated with a heavy material, and generally in a rectangular shape. Two opposing side edges of the block have semicircular interengaging members. On one side there is formed a semicircular lobe, and on the opposing edge of the block there is formed a semicircular recess. In one embodiment, the lobe and recess are formed so that when fully interengaged, there exists a space between adjacent blocks. As the blocks are lifted by a cable to a catenary position, the lobe of one block becomes disengaged with the recess of a neighbor block, and the adjacent block corner edges become engaged. The corner edges of the blocks are rounded or beveled to provide a larger surface area to distribute the load forces extended between blocks when suspended in the catenary form.
The other opposing side edges of the erosion control block include edge configurations for providing a circuitous channel when the blocks are installed side-by-side. Two sides edge portions of the erosion control block each include parallel surfaces connected together by an angled edge section. This circuitous channel between adjacent blocks joins the circuitous channel of another adjacent pair of blocks by a lateral water channel. With this arrangement, the channel between the mattress is not straight, but rather is circuitous to thereby impede the flow of water therethrough.
In the described embodiment, two spaced-apart cable channels are formed between two edges of the block, and another pair of space-apart cable channels are formed between the other two opposing edges. The end of each cable channel, where it terminates at the side edge of the block, opens into a cable cavity to thereby accommodate the use of an anchor button and/or splice sleeve on a cable.